AB0149 RNA SEQUENCING OF SKIN BIOPSY SAMPLES REVEALS UNIQUE BIOLOGICAL PROCESSES AMONG SPECIFIC GROUPS OF ADULT PATIENTS WITH IgA VASCULITIS
Authors: M. Bajželj, M. Hladnik, T. D. Toluay, S. Sodin-Šemrl, A. Hocevar, K. Lakota
Journal: Annals of the Rheumatic Diseases (2022)

Background Immunoglobulin A vasculitis (IgAV) is a small vessel leukocytoclastic vasculitis, characterized by vascular IgA deposits, and clinically by skin, join, kidney and bowel involvement. Renal involvement, present in up to 84% of adult patients, is associated with an increased risk of progression to chronic kidney failure. A skin or renal biopsy is still the golden standard for diagnosis. Omics data from NCBI-GEO and Array Express databanks are lacking from IgAV samples of adult patients. Objectives Our aim was to perform RNA sequencing and to identify differentially expressed genes and dysregulated molecular pathways in the affected skin of adult IgAV patients with renal involvement, patients with skin-limited IgAV and healthy controls (HC). Methods Skin biopsy samples were collected from treatment-naive adult IgAV patients at time of diagnostic procedure: 1) skin-limited disease (n=3), 2), IgAV with renal involvement (n=3), and age-/sex-matched HC (n=3). RNA was isolated and 100 bp paired-end sequenced using the Illumina HiSeq 4000 platform (25.9 to 30.8 million reads were obtained per sample). Reads were mapped with Salmon tool against the human transcriptome (Ensemble Release 104). Differentially expressed genes (log2 fold change ≥ │1│, padj &lt; 0.05) were computed using the R package DESeq2. Data were clustered using principal component analysis (PCA), and KEGG pathway over-representation analysis (ORA) was performed with R package clusterProfiler. Results We identified 72 differentially expressed genes (34 up- and 38 down-regulated) between skin-limited IgAV and HC, while 686 genes were differentially expressed (421 up- and 265 down-regulated) in the affected skin between adult IgAV patients with renal involvement and healthy controls (HC). PCA distinguished between IgAV (renal and skin-limited) and healthy controls, suggesting specific transcriptome signatures in IgAV. 21 overlapping genes were differentially expressed in both groups of patients in comparison to HC. 196 genes were differentially expressed between IgAV patients with renal involvement compared to skin-limited IgAV. Genes, differentially expressed in patients with skin-limited disease were enriched in the oxidative phosphorylation (padj = 3.08 x 10 -5 ) and cell adhesion molecules (padj = 6.32 x 10 -4 ) KEGG Pathways. Differentially expressed genes in patients with renal involvement exhibited enriched KEGG Pathways involved in the ribosome (padj = 0 x 10 -7 ), the regulation of lipolysis in adipocytes (padj 9,066 x 10 -4 ), cell adhesion molecules (padj = 8.0008 x 10 -3 ), renin secretion (padj = 4.2882 x 10 -3 ), complement and coagulation cascades (padj = 3.58547 x 10 -2 ), vascular smooth muscle contraction (padj = 3.76132 x 10 -2 ) and aldosterone synthesis and secretion (padj = 3.76132 x 10 -2 ). Conclusion Deregulated genes in skin of adult IgAV patients with renal manifestation could serve as biomarkers for organ-specific involvement. Further studies are needed that would support deciphering the involvement of perturbed molecular pathways and the contribution of individual cell types to skin manifestations of adult IgAV patients. Acknowledgements The authors also wish to thank all the patients who volunteered to participate into this study and the funding. Disclosure of Interests None declared